As “cloud computing” further develops, various cloud platforms have been introduced to satisfy user demand for “cloud services.” The cloud platforms utilize virtualization technology to share or monopolize central processing units (CPUs), memory, hard disks, and other hardware resources. As an example, in a cloud platform, a physical machine has virtual machines having different corresponding service ranks. Each virtual machine has a plurality of virtual disks, and each virtual disk has reading and writing input and output (I/O) ports, i.e., virtual disk I/O ports. Typically, the reasons that the virtual machines having the different service ranks are activated on a physical machine are twofold: 1) to satisfy diverse user requirements; and 2) to increase hardware resource utilization of the physical machine. In the cloud platform, actual processing of data reading-writing requests include a fair competition model-based technique of limited I/O reading, writing, and sharing, i.e., a first come first served method. However, in virtual machines with different ranks, a fair competition reading and writing model for limited I/O bandwidth can be somewhat unfair in terms of cost and benefit. For example, a user may pay a higher price to run a service with a higher service rank; however, because processing I/O operations are the same across the virtual machines, the user does not receive the benefits of a higher I/O rate even though the user has paid more. In addition, because applications from different types of business have different I/O bandwidth requirements, cloud platforms should perform I/O scheduling based on real-time I/O bandwidth resource expectations. For example, web-based applications typically expect that high-throughput, low-delay I/O bandwidth service is provided. Yet, some log-recording services often function adequately with low-throughput, high-delay I/O bandwidth service.
A majority of the currently existing cloud platforms share a plurality of virtual machines of I/O reading and writing of a single virtual disk, and the virtual disk is typically located on a physical disk of the physical machine. However, in the cloud platform, the virtual disks used by the virtual machines are not necessarily located on the disks of the physical machine where the virtual machines are located. Instead, the virtual machines can be distributed across an entire cluster of physical machines. Because of the distributed nature of the virtual machines, control over I/O operations of the virtual disk cannot be easily added to a physical disk of the local physical machine or to the operating system core of the local physical machine.